Various fuels may be used in engines. For example, gasoline, alcohol, and/or gasoline/alcohol blends may be used in an internal combustion engine in order to reduce emissions or utilize petroleum substitute fuels. Approaches are known to detect alcohol concentration in fuels so that engine operation may be adjusted accordingly, e.g., so that fuel injection amount may be adjusted.
However, typical approaches to detecting fuel alcohol (e.g., ethanol) concentrations with a degree of certainty and under a range of conditions may be difficult and/or expensive to perform. For example, in some approaches a direct ethanol sensor in the fuel tank or fuel delivery lines may be employed to determine ethanol content of the fuel. However, such approaches may be expensive due to the costly sensors employed. Other approaches may include steady-state comparisons of air/fuel ratios used to get an oxygen sensor to read stoichiometry. However, such approaches may have many noise factors and may rely on restrictive entry conditions to achieve steady-state.
The inventors herein have recognized that crankshaft accelerations may be used to identify the alcohol content of fuel used in an engine. In one example approach, a method of using crankshaft acceleration to identify the alcohol content of fuel comprises adjusting fuel injection to the engine based on fuel alcohol content identified from crankshaft acceleration. For example, the crankshaft acceleration may be generated by modulating an air/fuel ratio in a selected cylinder across a range of air/fuel ratios while keeping the engine at stoichiometry. The fuel alcohol content may then be identified based on a slope of a mapping of the crankshaft accelerations versus the modulated air/fuel ratios, for example.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.